1. Field of the Invention
The present invention relates to an exposure apparatus, a structure, a method for setting up an apparatus, and a device manufacturing method, which are particularly suitably used for a semiconductor manufacturing apparatus, a liquid crystal substrate manufacturing apparatus, a magnetic head manufacturing apparatus, and a micromachine manufacturing apparatus.
2. Description of the Related Art
Recently, in accordance with high integration of semiconductor devices, the resolution required for a semiconductor exposure apparatus is higher. In order to improve the resolution, NA (numerical aperture) equal to or greater than 0.9 is required for a projection optical system. Therefore, the projection optical system is getting larger. Furthermore, in order to improve the performance, it is necessary to suppress a disturbance such as a vibration. As a result, in order to improve the stiffness of the apparatus, the apparatus gets larger and the weight of the apparatus also increases.
FIG. 5 is a configuration of an exposure apparatus which is disclosed in Japanese Patent Laid-Open No. 11-297587. A lens-barrel platen 10 which supports a projection optical system 9 is supported by an active mount 12 including an actuator for reducing a vibration. A Z-interferometer 16 and an XY-interferometer 17 for measuring a position of a wafer stage 7 which mounts a wafer 6 are attached to the lens-barrel platen 10.
The Z-interferometer 16 and the XY-interferometer 17 measure a relative position of the wafer stage 7 with respect to the projection optical system 9. Based on the measurement result, the wafer stage 7 is positioned. The active mount 12 is supported on an apparatus support leg and the apparatus support leg is directly supported on an apparatus setting floor.
As described above, in a method for directly setting up the apparatus on the setting floor, the floor is subducted by the increase of the weight of the apparatus in accordance with growth in size of the apparatus and by the point contact between the setting leg of the apparatus and the setting floor caused by a local irregularity of the floor surface. Usually, since the floor on which the apparatus is set up is made of concrete, in the case of the point contact, the force acting on the concrete may exceed a load capacity or an intensity of the concrete. The subduction amount is different by the difference of the load distribution of the apparatus or the difference of the state of the floor, and an ideal apparatus attitude can not be duplicated. Furthermore, when the subduction of the floor occurs, the attitude of the apparatus changes and a distortion such as a twist of the structure of the main body of the exposure apparatus occurs, which is led to the performance degradation.
Recently, in order to respond to a miniaturization requirement which is required for the semiconductor exposure apparatus, the requirement for the vibration environment is stricter. In particular, an exposure apparatus called a scanner synchronously scans a wafer stage placing a semiconductor wafer and a reticle scan stage placing a reticle that is an original of a circuit pattern in opposite directions to each other with a predetermined velocity ratio, and the exposure is performed during the scan. Therefore, when the disturbance due to a vibration occurs in the synchronous scan, the quality of manufactured ICs is significantly deteriorated. In other words, the scanner is extremely sensitive to the vibration of the floor on which the scanner is set up, or the like.
Conventionally, with respect to the vibration of the floor in a clean room where the semiconductor exposure apparatus is set up, it is considered that a basis called a pedestal is laid and the overall exposure apparatus is set up on it. However, even if the pedestal which has a large amount of weight and an appropriate decay action is laid in order to reduce the vibration which intrudes into the scanner, the intrusion of the vibration can not be fully blocked. Furthermore, a setting surface of the setting leg part of the apparatus jounces and a vibration problem occurs because of the local irregularity of the setting floor surface. This vibration is transmitted to the interferometer or the projection optical system in the main body of the exposure apparatus from the setting leg. In other words, the vibration from the setting floor can not be adequately reduced by the active mount equipped with the conventional exposure apparatus, and it is transmitted to each unit of the exposure apparatus via the setting leg and the platen. This negatively affects the positioning accuracy of the wafer stage which controls the position so that the signal from the interferometer indicates a target value or the exposure performance of the projection optical system.
In the latest pedestal, although the irregularity of the concrete surface may be smoothed by machining or polishing, there is a problem that it takes extremely much cost and lead time. Furthermore, the pedestal can be processed only when it is alone before it is set up in the clean room. Therefore, if the overall pedestal is tilted at the time of setting up the pedestal in the clean room, the setting surface of the apparatus is also tilted. In this case, the main body of the semiconductor exposure apparatus usually performs a leveling using a level. Therefore, if the overall pedestal is tilted, the setting leg of the apparatus and the setting surface of the pedestal are in contact with each other by a point after all.
The apparatus needs to keep an initial setting state for a long time. Generally, in the case of a large apparatus, there is great possibility that the setting floor is subducted because the weight of the apparatus is great. Furthermore, the change of the floor with the passage of time is also concerned by using the apparatus for a long time.